The first man-made plastic was invented in Britain in 1851 by Alexander Parkes. He publicly demonstrated it at the 1862 International Exhibition in London, calling the material Parkesine. Derived from cellulose, Parkesine could be heated, molded, and retain its shape when cooled. It was, however, expensive to produce, prone to cracking, and highly flammable. In 1868, American inventor John Wesley Hyatt developed a plastic material he named Celluloid, improving on Parkes' invention so that it could be processed into finished form. Hyatt patented the first injection molding machine in 1872. It worked like a large hypodermic needle, using a plunger to inject plastic through a heated cylinder into a mold. The industry expanded rapidly in the 1940s because World War II created a huge demand for inexpensive, mass-produced products. In 1946, American inventor James Watson Hendry built the first screw injection machine. This machine also allowed material to be mixed before injection, so that colored or recycled plastic could be added to virgin material and mixed thoroughly before being injected. In the 1970s, Hendry went on to develop the first gas-assisted injection molding process.
Injection molding machines include a material hopper, an injection ram or screw-type plunger, and a heating unit. They are also known as presses, and they hold the molds in which the components are shaped. Presses are rated by tonnage, which expresses the amount of clamping force that the machine can exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than 5 tons to 6000 tons, with the higher figures used in comparatively few manufacturing operations. The total clamp force needed is determined by the projected area of the part being molded. This projected area is multiplied by a clamp force of from 2 to 8 tons for each square inch of the projected area. As a rule of thumb, 4 or 5 tons per square inch can be used for most products. If the plastic material is very stiff, it will require more injection pressure to fill the mold, thus more clamp tonnage to hold the mold closed. The required force can also be determined by the material used and the size of the part, since larger parts require a higher clamping force. With injection molding, granular plastic is fed by gravity from a hopper into a heated barrel. As the granules are slowly moved forward by a screw-type plunger, the plastic is forced into a heated chamber, where it is melted. As the plunger advances, the melted plastic is forced through a nozzle that rests against the mold, allowing it to enter the mold cavity through a gate and runner system. The mold remains cold so the plastic solidifies almost as soon as the mold is filled.
Mold assembly or die are terms used to describe the tooling used to produce plastic parts in molding. The mold assembly is used in mass production where thousands of parts are produced. Molds are typically constructed from hardened steel, etc.
Hot-runner systems are used in molding systems, along with mold assemblies, for the manufacture of plastic articles. Usually, hot-runner systems and mold assemblies are treated as tools that may be sold and supplied separately from molding systems.
It is known to use hot-runner systems in injection molding systems.
U.S. Pat. No. 4,831,230 (Inventor: Lemelson, Jerome H.; Filed: Nov. 26, 1986) discloses “an apparatus and method for shaping and surface finishing articles and material of manufacture by means of intense radiation.”
U.S. Pat. No. 4,929,402 (Inventor: Hull, Charles W.; Filed: 19 Apr. 1989) discloses “a system for generating three-dimensional objects by creating a cross-sectional pattern of the object to be formed at a selected surface of a fluid medium capable of altering its physical state in response to appropriate synergistic stimulation by impinging radiation, particle bombardment or chemical reaction, successive adjacent laminae, representing corresponding successive adjacent cross-sections of the object, being automatically formed and integrated together to provide a step-wise laminar buildup of the desired object, whereby a three-dimensional object is formed and drawn from a substantially planar surface of the fluid medium during the forming process.”
U.S. Pat. No. 4,575,330 (Inventor: Hull, Charles W; Filed: 8 Aug. 1984) discloses “a system for generating three-dimensional objects by creating a cross-sectional pattern of the object to be formed at a selected surface of a fluid medium capable of altering its physical state in response to appropriate synergistic stimulation by impinging radiation, particle bombardment or chemical reaction, successive adjacent laminae, representing corresponding successive adjacent cross-sections of the object, being automatically formed and integrated together to provide a step-wise laminar buildup of the desired object, whereby a three-dimensional object is formed and drawn from a substantially planar surface of the fluid medium during the forming process.”
U.S. Pat. No. 5,204,055 (Inventor: Sachs, Emanuel M., et al.; Filed: 8 Dec. 1989) discloses “a process for making a component by depositing a first layer of a fluent porous material, such as a powder, in a confined region and then depositing a binder material to selected regions of the layer of powder material to produce a layer of bonded powder material at the selected regions. Such steps are repeated a selected number of times to produce successive layers of selected regions of bonded powder material so as to form the desired component. The unbonded powder material is then removed. In some cases the component may be further processed as, for example, by heating it to further strengthen the bonding thereof.”
U.S. Pat. No. 5,121,329 (Inventor: Crump, Scott S., Filed: 30 Oct. 1989) discloses “apparatus incorporating a movable dispensing head provided with a supply of material which solidifies at a predetermined temperature, and a base member, which are moved relative to each other along “X,” “Y,” and “Z” axes in a predetermined pattern to create three-dimensional objects by building up material discharged from the dispensing head onto the base member at a controlled rate. The apparatus is preferably computer driven in a process utilizing computer aided design (CAD) and computer-aided (CAM) software to generate drive signals for controlled movement of the dispensing head and base member as material is being dispensed. Three-dimensional objects may be produced by depositing repeated layers of solidifying material until the shape is formed. Any material, such as self-hardening waxes, thermoplastic resins, molten metals, two-part epoxies, foaming plastics, and glass, which adheres to the previous layer with an adequate bond upon solidification, may be utilized. Each layer base is defined by the previous layer, and each layer thickness is defined and closely controlled by the height at which the tip of the dispensing head is positioned above the preceding layer.”
U.S. Pat. No. 5,775,402 (filed: Oct. 31, 1995; Inventor: Emanuel Sachs) discloses processes for providing enhanced thermal properties of tooling, particularly metal and metal/ceramic molds, made by solid free form fabrication techniques, such as the three dimensional printing process, and the tooling made by these processes are disclosed. The methods of enhancing thermal properties include incorporating integral contour coolant channels into the mold, adding surface textures to the coolant channels, creating high thermal conductivity paths between the surfaces and the coolant channels, and creating low thermal inertia regions in the mold.
European Patent Number 0863806 (Inventor: Freitag, et al.; Filed: 26 Nov. 1996) discloses “manufacturing of solid three-dimensional articles, and is more specifically directed to the additive fabrication of metal articles such as parts and mold dies.”
U.S. Pat. No. 7,047,098 (Inventor: Lindemann, Markus, et al.; Filed: 21 Feb. 2002) discloses “a process for producing a shaped body by selective laser melting, in which a shaped body is built up from pulverulent metallic material using CAD data of a model, in which a powder layer is applied using an applicator unit, and in which the applied powder layer is fixed to a layer below it using a focused laser beam, in which process the powder layer is leveled to a desired layer thickness as a result of a leveling device passing over the shaped body at least once, and during the leveling elevations that project above the desired layer height of the applied powder, of the layer which was last melted by the laser beam are uncovered by the leveling device.”
U.S. Pat. No. 7,381,360 (Inventor: Oriakhi, Christopher, et al.; Filed: 3 Nov. 2003) discloses “compositions, methods, and systems for solid free-form fabrication of three-dimensional objects.”
U.S. Pat. No. 7,220,380 (Inventor: Farr, Isaac, et al.; Filed: 14 Oct. 2003) discloses “a method for solid free-form fabrication of a three-dimensional metal object includes depositing a particulate blend in a defined region, the particulate blend including a number of metal or metal alloy particulates and a peroxide, and selectively ink-jetting a binder system onto a predetermined area of the particulate blend to form a green part, wherein the liquid phase binder includes a water soluble monofunctional acrylate-based monomer, a water soluble difunctional acrylate-based monomer, an amine, and water.”
United States Patent Publication Number: 2004/0079511 and U.S. Pat. No. 6,701,997 (filed 17 Jun. 2002; Inventor: Gellert, Jobst U, et al.) discloses: “(i) a process for fabricating an injection molding component having an electrical heating attached thereto, the process comprising the steps of: contacting the electrical heating element with a powdered metal preform having at least partial open porosity, the powdered metal preform being composed of a first metal; contacting the preform adjacent a region of the open porosity with a mass of a second metal, the second metal having higher thermal conductivity than the first metal; heating the preform, the heating element and the mass so as to cause the second metal to at least partially infiltrate the open porosity of the preform and at least partially join the heating element to the preform when cooled, (ii) a process for fabricating a metal part having at least two components, the process comprising the steps of: making a powdered preform of a first component, the preform having at least partial open porosity; contacting a second component with the preform of the first component; and infiltrating the open porosity of preform with a second metal wherein the second component is brazed to the first component by the second metal substantially contemporaneously with the infiltration step, (iii) a process for fabricating a metal part having at least two components, the process comprising the steps of: making a powdered preform of a first component, the preform having at least partial open porosity; contacting a second component with the preform of the first component to form an assembly thereof; contacting the preform first component with a mass of a metal infiltrant; controllably heating the assembly and the metal infiltrant to melt the metal infiltrant; holding the assembly and the metal infiltrant at temperature until the open porosity of the preform of the first component is at least partially infiltrated by the metal infiltrant and the second component is at least partially brazed to the first component by the metal infiltrant; and controllably cooling the assembly to solidify the metal infiltrant, and (iv) a process for fabricating an injection molding component, the process comprising the steps of: mixing a powdered tool steel with a binder to form an admixture; injecting the admixture into a preform; debinderizing the preform; partially sintering the preform to achieve 40% to 10% volume open porosity therein; contacting the preform with a metal infiltrant, the metal infiltrant having high thermal conductivity; controllably heating the preform and the metal infiltrant to at least the melting temperature of the metal infiltrant; holding the preform and the metal infiltrant at temperature until the porosity of the first component is at least partially infiltrated by the metal infiltrant, and cooling the preform to solidify the metal infiltrant and yield the injection molding component.”
United States Patent Publication Number 2004/0169699 (Inventor: Hunter, Shawn, et al.; Filed: 28 Feb. 2003) discloses “a method of producing an object through solid freeform fabrication, said method comprising applying two immiscible fluids to a build material.”
U.S. Pat. No. 7,234,930 (Inventor: Niewels, et al; Filed: 14 Jun. 2004) discloses “a second piece is formed by a three-dimensional printing process or other powder forming technique such as investment casting. The three dimensional printing process or other powder forming techniques permit the formation of ideal cooling channels within the structure. This provides a neck ring half with high strength provided by the first piece and high thermal conductivity provided by the second piece.”
U.S. Pat. No. 7,326,377 (Inventor: Adams, Robbie J; Filed: 30 Nov. 2005) discloses “a solid free form fabrication system for manufacturing a component by successively building feedstock layers representing successive cross-sectional component slices includes a platform for receiving and supporting the feedstock layers, a feedstock supplying apparatus that deposits the feedstock into a predetermined region to form the feedstock layers, an energy source directed toward the predetermined region to modify the feedstock in the predetermined region and thereby manufacture the component, and a temperature control block disposed on the platform and directly in contact with the deposited feedstock layers to modify the feedstock temperature while manufacturing the component. A solid free form fabrication method uses the system to manufacture the component from the feedstock material.”
United States Patent Publication Number 2005/0186538 (Inventor: Uckelmann, Ingo; Filed: 24 Feb. 2005) discloses “a method for making metallic and/or non-metallic products 2, in particular dental products, by freeform sintering and/or melting.”
United States Patent Publication Number: 2009/0108500 (filing date: 31 Oct. 2007, inventor: Edward Joseph Jenko) discloses “Additionally, a low strength manifold, such as one made with low grade steel or through free form fabrication, can be used in the production of such molded pieces requiring high pressure injection.
United States Patent Publication number: US 2009/0192835 (filing date: 24 Jan. 2008; Inventor: Martin H. Baumann et al) discloses at paragraph [0023] “Additionally, a low strength manifold, such as one made with low grade steel or through free form fabrication, can be used in the production of such molded pieces requiring high pressure injection.”
A technical journal titled: HIGH PERFORMANCE PLASTICS (Issue: October 2005 on page 5; Title of Article: FREEFORM FABRICATION FOR PROTOTYPING) discloses “US researchers are developing an automated prototyping process in which an advanced composite is formed into a freestanding, three-dimensional object. The technique—called composite layer manufacturing (CLM)—does not require moulds, dies or other tooling. In addition, there is usually no need for machining, as the process creates net-shapes, the developers say.”
A technical journal titled: ADVANCED COMPOSITES BULLETIN (Issue: October 2005 on page: 10; Title of Article: SOLID FREE-FORM FABRICATION OF REINFORCED PLASTICS) discloses: “US researchers are developing an automated prototyping process in which an advanced composite is formed into a freestanding, three-dimensional object. The technique—called composite layer manufacturing (CLM)—does not require moulds, dies or other tooling. In addition, there is usually no need for machining, as the process creates netshapes, the developers say.”
A technical publication titled: HOT RUNNERS—PLATE FUSING TECHNOLOGY FOR DESIGNING AND BUILDING MANIFOLDS (Publication Date: April 2007; Author: Gilbert Chan; Publication: www.moldmakingtechnology.com) discloses how plate fusing technology can benefit the mold designer and mold maker. Specifically, most hot runner manifolds are plug style manifolds where the manifold starts out as a solid plate of steel and straight flows are gun drilled into the plate to create intersecting flow channels. Hot runner channel plugs are then used to plug the drilled holes and to create the final flow path. Manifolds manufactured in this fashion are limited to straight flows, hard 90-degree turns in flow, and typically contain steps between the flow channels and the plugs, which can create hold up areas for the material. A secondary operation to polish the manifold channel intersections involves using a slurry to smooth the flow surfaces, but because this is a blind method, smooth flows without steps are not always guaranteed. The plate-fusing technology provides a method for building a manifold. As the name suggests, plate fusing technology uses separate steel plates that are fused together to create a solid manifold. The process starts out with two or more plates. Flow channels are machined in the faces of the steel. These will become the internal surfaces of the manifold melt channel. These channels will be machined on a CNC (computer numerical control) mill with ball end mills to produce smooth, rounded flow channels with flowing radii at the transitions in the x-y plane but not in the z plane. The channels can vary in size and can travel between the levels of the plates but transitions from x-y plane to the z plane will still have abrupt or “hard” 90-degree turns.